There is a demand that wheat flour-containing foods including e.g. deep-fried foods, such as tempura etc., okonomiyaki (Japanese-style pancakes), and spongy confectionery, such as pancakes etc., should not undergo texture degradation over time after being heated and cooked or texture degradation when re-heated in a microwave oven etc., and should maintain an excellent biting sensation, meltability in the mouth, and a light texture equivalent to the sensation/texture obtained immediately after being heated and cooked. As a technique for obtaining a wheat flour-containing food satisfying the demanded characteristics, Patent Literature 1 discloses a process in which the pH of a fluid dough obtained from a cereal flour material including wheat flour as a main component is adjusted twice to fail within specific ranges.
Also, it has been conventionally known to subject cereal flour to a heating treatment with the aim of deactivation of enzymes in the cereal flour, sterilization of the cereal flour, and also quality improvement. For example, Patent Literature 2 discloses a wheat composition suitable for steamed food products, such as steamed buns or steamed bread. The wheat composition is obtained by: mixing a wheat flour and 0.1 to 2.0 parts by mass of an emulsifier (e.g. glycerol fatty acid ester) with respect to 100 parts by mass of the wheat flour; and then subjecting the mixture to an indirect heating treatment under conditions where the product temperature is from 80 to 150° C. and the heating time is from 5 to 120 minutes. In the indirect heating treatment, heated water vapor is used as a heat source, and the heated water vapor is not directly applied to the mixture including the wheat flour and the emulsifier, but is applied to a container containing the mixture, and the mixture inside the container is heated indirectly; here, the mixture is subjected to a dry-heat treatment, and not to a heat-moisture treatment. With the wheat composition disclosed in Patent Literature 2, it is possible to obtain a steamed food product having a soft, plump appearance and resilient tactile feel while offering a moist texture and meltability in the mouth. Also, it is disclosed that, even after being stored/distributed and re-steamed or heated in a microwave oven, the obtained steamed food product is capable of maintaining a soft, plump appearance and a melt-in-the-mouth texture without becoming hard.
Similar to Patent Literature 2, Patent Literature 3 also discloses an indirect heating treatment of a mixture including wheat flour and an emulsifier, and describes that it is possible to obtain an okonomiyaki premix that gives a dough capable of being cooked directly in a microwave oven.
Patent Literature 4 discloses a processed-food quality improving agent that is for improving quality such as texture and that is added to food materials with high moisture content or to food products whose texture is likely to become dry and stale as a result of the outflow of extract components when heated and cooked. The quality improving agent is obtained by heating and kneading cereal flour having a moisture content of from 10 to 40 wt % in the presence of an emulsifier at a product temperature of 55° C. or higher, to pregelatinize the starch component. It is also disclosed that the heating/kneading of the cereal flour is performed by using a uniaxial or biaxial screw-type extruder. According to Patent Literature 4, the processed-food quality improving agent disclosed in Patent Literature 4 has a swelling degree within the range of from 5.9 to 8; thus, this product is considered to be substantially equivalent to pregelatinized wheat flour.